A thermal blanket or cover for a swimming pool. The blanket consists of a covering of flexible plastic sheet material to which are secured strips of foam-backed plastic sheet material to provide flotation and reinforcement.

The invention consists in an immersible solar heat collecting means capable of being laid at the bottom of a pool where it can be walked upon. The substantially laminar portions of the collector each includes a surface of higher light absorbence than the other side thereof so that by folding or otherwise overlapping and rearranging the various portions a different number of higher light absorbence surfaces can be presented to the sun to heat the water at any particular time. Such an apparatus makes possible the controlled solar heating of a pool.

A pool cover (C2) for use in a swimming pool (S) to inhibit algae growth and make the pool water more readily usable when the cover is removed. The cover includes single or multiple, interconnected panels (P) sized to fit within the confines of the pool, regardless of pool size and shape. Each panel comprises a multiple layer of material including upper and layers (L1, L2) of opaque material with a buoyant material (B) between these layers. Side panels (N) attach to the main portion of the cover to cover water surface areas (W, A, V) where people enter the pool, wade, or sit. The cover is used in conjunction with a cover (C1) fitted over the pool to protect the pool and people moving around the pool during those times of the year when the pool is not in use. The two covers are used together in a pool cover system.

A foldable swimming pool cover includes, in one embodiment, a screen constructed of an ultra-fine, lightweight mesh fabric and a plastic frame mounted on the periphery of the screen. The plastic frame includes a plurality of frame members, each of the frame members having a pair of free ends. The free ends of adjacent frame members are pivotally connected by a bi-directional hinge assembly which enables the swimming pool cover to be collapsed into a vertical stack of individual panels in an accordion fashion. In use, the swimming pool cover is designed to be placed over a swimming pool to prevent environmental debris from falling into and contaminating the water held within the swimming pool. Because the screen is constructed of a mesh fabric, moisture will pass through the screen and environmental debris will accumulate on the screen. In order to use the swimming pool, the swimming pool cover can be folded into a vertical stack of individual panels and lifted off the pool.

A thermally insulative buoyant swimming pool cover floats on the surface of the pool for covering the pool and for retaining the heat within the pool. Sinking means, such as weights or a mechanical pull-down structure, is secured to the pool cover along certain predetermined action lines such as fold lines. In one embodiment, an inflatable and deflatable bladder is coupled to the weights. The bladder is dimensioned relative to the weights such that when inflated it overcomes the negative buoyancy of the weights to retain the pool cover in the fully covered position. However, when the bladder is deflated, the weights overcome the positive buoyancy of the cover along the certain fold lines causing the cover to be at least partially pulled below the surface of the pool and folded while at the same time being retracted against one of the side walls of the pool. Pool water is circulated over or through channels of the pool cover to provide solar heating. Pool water is circulated over the top of the cover for cleaning thereof. The weights are preferably hollow to receive the inflatable bladders. Air permeable structures are contained within the bladders to obtain more uniform inflation thereof. The lip of the cover contains additional positive buoyancy for additional support at the lip.